A. Field of the Invention
The embodiments of the present invention relate to a method of making an ultra-wideband coupling capacitor, and more particularly, the embodiments of the present invention relate to a method of making an orientation-insensitive ultra-wideband coupling capacitor.
B. Description of the Prior Art
To fully realize the accomplishment of the method of the embodiments of the present invention, it would be most beneficial to discuss the state of the art of the ultra-wideband coupling capacitors for which the orientation-insensitive ultra-wideband coupling capacitor produced by the method of the embodiments of the present invention surpasses.
As shown in FIGS. 1 and 2, which are, respectively, a schematic diagram of a prior art ultra-wideband coupling capacitor, and, an exploded diagrammatic perspective view of a prior art ultra-wideband coupling capacitor, a prior art ultra-wideband coupling capacitor 10 is a parallel combination of a high value capacitor 12, typically 10 nanofarads or greater, and a low value capacitor 14, typically 20 picofarads to 250 picofarads. As can be seen, capacitors in parallel result in wider operating bandwidths.
The prior art ultra-wideband coupling capacitor 10 is either composed of two or more physical items requiring precise assembly or a single ceramic assembly that must internally include complex multiple capacitor configurations, and via holes that interconnect internal electrodes to external contacting pads. Both of these family of devices have larger than desired physical footprints and can only be mounted on one specific side of the device making them difficult to use where surface mount technology (SMT) is employed. Electrically, size limitations result in both high insertion and return losses and also cause excessive surface moding at higher microwave frequencies.
The high value capacitor 12 is a multi-layer capacitor, while the low value capacitor 14 is generally either a single layer capacitor or two single layer capacitors in a balanced configuration. The multi-layer capacitor is a multi-layer structure with interdigitated plates, each separated by a thin dielectric layer, while the single layer capacitor is a single layer structure with two plates separated by a thin dielectric layer.
The high value capacitor 12, with its relatively low series resonance is most effective on low frequency signals, while the low value capacitor 14 with its relatively high series resonance is most effective on high frequency signals.
The high value capacitor 12 and the low value capacitor 14 of the prior art ultra-wideband coupling capacitor 10 have different operating characteristics in different portions of an ultra-wideband operating spectrum as will be discussed below.
As shown in FIG. 3A, which is a schematic diagram of a prior art ultra-wideband coupling capacitor operating at a low frequency, when the prior art ultra-wideband coupling capacitor 10 is operating at a low frequency, the prior art ultra-wideband coupling capacitor 10 electrodes exhibit insignificant skin effect. The ceramic structure looks like a bulk dielectric.
As shown in FIG. 3B, which is a schematic diagram of a prior art ultra-wideband coupling capacitor operating at a mid frequency, when the prior art ultra-wideband coupling capacitor 10 is operating at a mid frequency, the prior art ultra-wideband coupling capacitor 10 electrodes exhibit significant skin effect. The dielectric region begins to take on the effect of a meandering parallel plate transmission line structure. Additional resonances emerge.
As shown in FIG. 3C, which is a schematic diagram of a prior art ultra-wideband coupling capacitor operating at a high frequency, when the prior art ultra-wideband coupling capacitor 10 is operating at a high frequency, the prior art ultra-wideband coupling capacitor 10 electrodes exhibit full skin effect. The dielectric region acts as a loosely meandering parallel plate transmission line. Additional resonances emerge at the higher frequencies.
The prior art ultra-wideband coupling capacitor 10 has a few associated shortcomings. Firstly, since the prior art ultra-wideband coupling capacitor 10 is a two-piece structure, the prior art ultra-wideband coupling capacitor 10 requires additional production assembly effort increasing per unit cost. Secondly, the prior art ultra-wideband coupling capacitor 10 is orientation-sensitive restricting it to being mounted only on one specific surface creating surface mount technology (SMT) compatibility issues. Thirdly, the assembly height of the prior art ultra-wideband coupling capacitor 10 exceeds the 0.020″ dimension of a standard 0402 package by 0.012″.
Thus, there exists a need for an ultra-wideband coupling capacitor which is one-piece and thereby eliminates additional production assembly effort thereby decreasing per unit cost, which is orientation-insensitive and thereby eliminates restricting it to being mounted only on one specific surface thereby eliminating surface mount technology (SMT) compatibility issues, and which does not exceed the 0.020″ dimension of a standard 0402.
Numerous innovations for high frequency capacitors have been provided in the prior art, which will be discussed below in chronological order to show advancement in the art, and which are incorporated herein by reference thereto. Even though these innovations may be suitable for the specific individual purposes to which they address, they each differ in structure, and/or operation, and/or purpose from the embodiments of the present invention.
(1) U.S. Pat. No. 5,576,926 to Monsorno.
U.S. Pat. No. 5,576,926 to Monsorno has an assignee common with the instant application and presents a capacitor having a superior ability to operate in the upper regions of the RF spectrum. The capacitor includes a planar electrode layer that is mounted between a pair of dielectric layers. The electrode layer generally is centered inwardly with respect to the dielectric layers leaving an outward margin of dielectric material. One of the dielectric layers has two spaced-apart contact members, each having a different polarity from the other. The electrode layer is isolated from electrical contact with any conductor and is buried within the dielectric layers. The electrode layer in combination with the dielectric layer on which the contact members are mounted and the contact members allow development of a selected value of capacitance between the contact members. Providing trimmed contact members, as well as controlling their size and spacing, allow for convenient preselection of desired operative characteristics of the capacitor. The contact members could be positioned on a substrate to which a buried electrode is mounted.
(2) U.S. Pat. No. 6,690,572 to Liebowitz.
U.S. Pat. No. 6,690,572 to Liebowitz teaches an SLC having a thin brittle ceramic dielectric layer less than 0.0035 inches thick and as low as 0.0005 inches or less. Electrodes are thick and strong enough, either singly or together, to give the structure required physical strength for manufacture, handling, and usage. Electrodes are either a ceramic metal composite, a porous ceramic infiltrated with metal or other conductive material, a resin filled with metal or other conductive material, or combinations of the above. The very thin and in itself fragile dielectric layer provides exceedingly high capacity per unit area with temperature stability and low losses. A 0.00001-inch thick dielectric of titanium dioxide is also used.
It is apparent that numerous innovations for high frequency capacitors have been provided in the prior art that are adapted to be used. Furthermore, even though these innovations may be suitable for the specific individual purposes to which they address, they would not be suitable for the purposes of the embodiments of the present invention as heretofore described.